A graphene is a two-dimensional nanomaterial composed of carbon atoms. This material has remarkably excellent properties such as a high current-density resistance, an ultrahigh mobility, a high heat resistance, and a high mechanical strength, and therefore has been regarded as a promising wiring material for a semiconductor device similarly to a carbon nanotube. For example, a graphene nanoribbon shaped into a width of about 10 nm is theoretically expected to have an electrical conductivity higher than that of copper. Under the circumstance, studies have been made on the use of the graphene in wirings. A single-layered graphene sheet cannot have a low resistance similar to that of a metal, and a multi-layered graphene sheet with a large area has to be produced at a low temperature to realize the low resistance.
Currently, the multi-layered graphene sheet with a large area is generally produced by growing the graphene on a thin film of a catalytic metal such as Ni, Fe, or Co at a high temperature of 800° C. or higher in a CVD process. From the viewpoint of suitability for semiconductor processes, the catalytic metal is desirably Ni or Co, and the growth temperature is desirably 600° C. or lower.